Flip through the book in Night Light, which tells the backstory of the two kittens. They made noise and played pranks, so much so that they angered one wizard. He cast a spell on the kids, as a result of which they now cannot meet, because one of them can only move in the dark, and the other in the light. The exposure of dark to light and light to darkness will lead to their disappearance. Heroes need to complete all levels to remove the spell. Each hero must get to the door of his own color. As the heroes move, the shadows will shift and thus you can move your friends to reach the desired door in Night Light.
